The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Vic Islamic Council against terror laws

Teen terror suspects as young as 14 could be locked up for two weeks without charge as Victoria reacts to its most recent terror attack.

But the Islamic Council of Victoria has already warned against locking up radicalised youths, saying it has a "dampening effect on Australian Muslims' freedom of religion".

Terrorist Yacqub Khayre, 29, killed one man and injured three police officers in Brighton on June 5, telling a TV station he was doing it for Islamic State and al-Qaeda.

Premier Daniel Andrews said he had spoken to police about the "gaps" in dealing with teen terror suspects who pose an unacceptable risk.

"Now it is time to look at additional powers. We will make changes that will not be universally popular because it is our judgement that is what is needed," he told reporters on Tuesday.

"We will have proper oversight. It will be a responsible package of measures and we will have more to say on that soon.

"The challenge is, of course, those who present as a potential threat that may not yet have committed a criminal act, or their past may not be closely associated with terror so those national powers don't kick in."